Uphill screen printing in the manufacturing of microelectronic components

ABSTRACT

Method for screen printing a continuous structure on a substrate wherein the screen printed structure extends from at least a first level to at least a second level. The disclosed method is particularly suitable for the fabrication of microelectronic devices and components thereof including the fabrication of field emission display devices. Preferably, a print screen of a preferred thickness having a preconfigured print pattern formed therethrough, in combination with a squeegee having a hardness within a preferred range, are used to force a screen printable substance onto a substrate while maintaining a portion of the print screen within a preferred reference angle. The resulting screen printed structure extends from at least one lower level to at least one upper level in a continuous “uphill” manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/152,257,filed May 21, 2002, now U.S. Pat. No. 6,736,058, issued May 18, 2004,which is a continuation of application Ser. No. 09/650,840, filed Aug.30, 2000, now U.S. Pat. No. 6,439,115, issued Aug. 27, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to microelectronic devices and the manufacturingthereof, including, but not limited to, the manufacturing of fieldemission, or effect, display (FED) devices. More particularly, thisinvention relates to the screen printing of screen printable substancesonto various substrates to form, for example, electrically conductivetraces, or conductor elements, on selected components of microelectronicdevices such as, but not limited to, substrates incorporated within FEDdevices.

2. State of the Art

Screen printing is frequently used within the microelectronic industryin the manufacturing of a wide variety of microelectronic components andproducts. For example, various electrical circuits, or traces, can beformed on a selected planar, rigid substrate by screen printing toprovide a wide selection of electrical circuitry and circuit functions.Such screen printed electrical circuits can include, for example,conductive elements and paths, resistive elements and paths, as well asvarious elements that have certain preselected insulative or dielectriccharacteristics or qualities. Thus, the term “conductive” as used hereinbroadly refers to any material capable of conducting electricity.

In the fabricating of field emission displays, or flat-panel displays,the microelectronic industry faces a constant demand by the market tomake such displays thinner and lighter and generally more compactcompared to the previous generation of displays. Furthermore, there isconsiderable market pressure for manufacturers to generally makemicroelectronic devices, including field emission displays, for example,more quickly and less expensively in order for companies sellingproducts incorporating such microelectronic devices to be, and remain,competitive in the marketplace.

U.S. Pat. Nos. 5,766,053 and 5,537,738 each issued to Cathey et al.,assigned to the present assignee, and which are incorporated byreference herein, disclose an exemplary internal flat-panel fieldemission display and exemplary methods of attaching and electricallyconnecting inwardly facing planar substrates having matching patterns ofbond pads, respectively. In both of these patents, selected elevatedbond pads located on top of an insulative spacer, or ridge, which isprovided along a selected edge of the lower-most substrate, areelectrically connected by wire bonds to respectively associated circuittraces which were previously disposed upon the lower-most substrate soas to terminate short of the insulative spacer and be adjacent andlocated below the respectively connected elevated bond pads. In bothpatents, the respective electrical traces and the insulative spacer, orridge, were formed by the screen printing of conductive and dielectricscreen printable materials.

Exemplary prior known screen printing processes used in the formation ofmicroelectronic components include the printing of conductive layersupon a selected substrate by forcing a paste, or printable substance, ofa preselected viscosity through a stainless steel or, more often, amonofilament polymer screen of a preselected mesh having a preselectednegative pattern formed through the screen by various known methods. Thescreen having a preselected pattern preformed therethrough is stretchedso as to be tautly secured to a support frame such that the screen andthe substrate can eventually be brought into very close proximity,preferably just short of actual direct contact with each other. Upon thescreen being precisely positioned above the substrate in which thescreen printable substance is to be disposed, the screen printablesubstance is typically introduced on top of the screen and a squeegee,or rubber blade, is biased toward the substrate and is swept across theflexible screen thereby pushing the printable substance forward alongthe screen as well as forcing a portion of the screen printablesubstance downward through the negative pattern provided on the screenand onto the underlying substrate. After the printable substance hasbeen disposed on the receiving surface of the substrate and the screenand squeegee have been lifted away therefrom, the screen printedsubstance, or paste, is typically dried by firing at a selectedtemperature and duration. Thereafter, the substrate can be readied forfurther screen printing. For example, a dielectric layer maysubsequently be screen printed on top of an underlying, previouslyscreen printed conductive layer, or upon the last screen printedsubstance being fired, and the screen printed substrate may be forwardedon for further post-screen printing processing.

With respect to the fabrication and operation of field emission displaysin particular, typically, a cathode plate having a plurality ofindividual cathodic electrodes is positioned in a parallel, spaced apartrelationship with a transparent display substrate covered by aphosphorous film acting as an anode plate. Borosilicate glass is oftenselected as a transparent substrate due to its having a compatiblecoefficient of thermal expansion and suitable structuralcharacteristics. The two plates are spaced away from each other by atleast one dielectric spacer, ridge, or rail, which borders at least aportion, if not the entire periphery, of what is to be the display areaor window. Upon providing electrical potentials of appropriatepolarization and magnitude to various electrodes located on the cathodeplate, electrons are emitted therefrom and are drawn toward theopposing, but spaced-apart, glass substrate serving as an anode platewhereon images can be viewed through the display window. In order forthe opposing cathode plate and the transparent glass substrate/anodeplate to function properly, the very small space between the two platesmust be uniform and the various thickness of each of the various layersof screen printed material provided on each plate must be controlledwithin strict dimensional tolerances. Such strict dimensional tolerancesare needed, not only for keeping the final FED unit as thin as possible,but are also needed for quality control purposes of the image to bedisplayed. For example, various qualities of the displayed image, suchas overall image uniformity, resolution, and brightness, can be directlyinfluenced by minute, or out of specification, spacing of the twoopposing plates.

U.S. Pat. No. 5,612,256 issued to Stansbury, incorporated by referenceherein, is directed toward multi-layer electrical interconnectionstructures and fabrication methods. More particularly, the '256Stansbury patent discloses a flat-panel field emission display wherein adielectric connector ridge having a generally planar top surface withgenerally curved side surfaces, is screen printed onto the rear surfaceof a faceplate of an FED device. The faceplate is also provided with aplurality of lower-level electrically conductive connectors by way ofconventional screen printing that extend generally perpendicular to, andare spaced along one side but terminate short of, the dielectricconnector ridge. Preferably, a plurality of discrete upper-levelconnectors ultimately positioned in registry with the lower-levelconnectors are screen printed atop the dielectric connector ridge in asubsequent screen printing process. In due course, each of theupper-level connectors, and the corresponding discrete lower-levelconnectors, are, respectively, electrically interconnected by a bondwire, for example, in accordance with a preferred embodiment disclosedtherein.

Such a representative wire bonded connection in the context of arepresentative portion of an anode plate 16 of a field emission displayis shown in drawing FIGS. 1A through 1C of the present drawings. Moreparticularly in drawing FIG. 1A hereof, anode plate 16 has a transparentglass substrate 2 serving as an anode baseplate. Mounted upon substrate2 is a first layer of a dielectric material 4. Mounted on top ofdielectric layer 4 is an optional second dielectric layer 6 that isusually precision trimmed or polished to provide an upper planar surfacethat is of a specific height above the substrate, typically on the orderof 10 mils (0.010 inches/0.254 mm) in height. Thus, dielectric layers 4and 6 taken together, form a dielectric or insulative ridge 3, alsoreferred to as an insulative spacer or rail. Lower level conductiveelement or trace 8 is located on substrate 2. Lastly, a bond wire 12 isbonded at bond points 14 to provide an electrically conductive pathbetween lower-level conductive trace 8 and upper-level conductive trace10.

Illustrated in drawing FIGS. 1B and 1C hereof is the screen printingprocess of forming conductive traces 8 and 10 on a portion of arepresentative substrate, which in the case of an FED serves as an anodeplate 16 shown in drawing FIG. 1A. In drawing FIG. 1B, the ridge orspacer 3, comprising vertically stacked dielectric layers 4 and 6, haspreviously been formed onto substrate 2 by screen printing processesknown within the art. A screen printing apparatus 18, including a screensupport frame 20 and a flexible screen 22, is biased toward substrate 2by a squeegee 24. The arrow depicts the direction in which squeegee 24is moved across the top of screen 22, usually at a constant speed,thereby forcing conductive paste 26 downward through a pattern in screen22 and onto the exposed surface of substrate 2, thus forming lower-levelconductive trace 8. Illustrated in drawing FIG. 1C is the forming ofupper-level conductive trace 10 by squeegee 24 flexible screen 22downward to nearly press against the top of layer 6 while simultaneouslymoving forward, thereby causing conductive paste 26 to be laid down onthe exposed surface of layer 6 through a preformed pattern in screen 22.Note that conductive trace 8 stops short of the proximate edges ofdielectric layers 4 and 6 which form elevated ridge or rail 3 so thatscreen 22 does not unduly contact ridge 3 while forming lower-levelconductive trace 8.

Although the '256 Stansbury patent depicts in drawing FIG. 6 thereof,and discusses in column 5 of the specification thereof, that acontinuous terminal conductor having a lower-level base portionpositioned directly on the rear surface of the faceplate, and anupper-level connecting portion positioned atop the dielectric connectorridge, can be screen printed in a continuous manner onto both surfaces,the specification in column 8 states that, in practice, it isimpractical to screen print such continuous terminal conductors over theabrupt elevational change presented by the connector ridge. It is alsonoteworthy that the connector ridge depicted in drawing FIG. 6 of the'256 patent has a rounded or curved side profile and, clearly, does notinclude a substantially abrupt vertical, or substantially straight, sideprofile extending perpendicular to substrate 2.

Thus, there remains a need within the art for effective, practicalscreen printing processes and apparatus that can be used by the art toscreen print screen printable substances, such as electricallyconductive pastes, to form small, dimensionally close-tolerancedcontinuous multi-level conductive traces, or conductive elements,especially suitable for use in the manufacturing of microelectronicdevices, such as field emission display devices manufactured onhigh-speed production lines.

There further remains a need within the art for effective, practicalscreen printing processes and apparatus that can be used to formmulti-level conductive traces, or conductive elements, suitable for usein the fabrication of microelectronic devices which require less timeand fewer fabricating steps, thereby lowering the costs associated withmanufacturing microelectronic devices such as field emission displays.

A still further need within the art includes the need formicroelectronic devices and products which incorporate components havingscreen printable substances disposed thereon by screen printingprocesses and apparatus that offer enhanced versatility and capabilitycompared to prior known screen printing processes and apparatus.

BRIEF SUMMARY OF THE INVENTION

The present invention provides the ability to form, to close dimensionaltolerances and geometries, electrically conductive traces or otherstructures that extend from one level to at least one other elevatedlevel by the screen printing of screen printable substances, such as,but not limited to, conductive pastes of preselected viscosities.Preferably, the subject invention includes the screen printing of ascreen printable material upon a generally planar substrate to form aconductive trace thereon. The screen printing continues in an “uphill”manner to extend the conductive trace upward onto at least one elevatedsurface located above the underlying substrate. The present invention isparticularly suited for, but not limited to, the formation ofmulti-level conductive traces used in providing an electricallyconductive path from a first level to at least one second elevated levelin microelectronic devices.

The present invention is particularly useful in the fabrication offlat-panel field emission displays (FED) in which a first transparentsubstrate made of borosilicate glass is provided with an insulativestructure or spacer, also referred to as a ridge, rail, or similarstructure, made of a preselected dielectric material. The insulativespacer can extend upwards of 10 mils (0.010 inches/0.025 cm) from theunderlying glass substrate. In the preferred embodiment, a continuousconductive trace having a preselected geometry, such as a generallyrectangular shape, is applied to the substrate by way of a squeegeebeing biased against and traversing a screen having preformed patterns,or openings, therein. Preferably, the screen is very thin incross-sectional thickness, of the magnitude of 0.2 mils (0.0002inches/0.0005 cm) for example, and when finally positioned, ispreferably positioned to have a preferred snap-off distance, of themagnitude of 0.1 to 0.125 mils (0.0001 inches/0.0003 cm to 0.000125inches/0.00037 cm) for example, being maintained between the bottom ofthe screen and the top of the substrate or other surface in which thescreen printable material is to be disposed upon. A very soft squeegee,that is, a wiper or blade having a comparatively low durometer value, isused in combination with the thin screen to sweep the screen printablesubstance of a preselected viscosity through the screen and onto thesubstrate and up onto the top of the spacer in preferably a continuousuninterrupted fashion to preferably form a discrete, continuous bi-levelor multi-level conductive trace, or another similarly formed structure.

Preferably, the angle of the screen with respect to the top surface ofthe spacer is maintained at a preselected angle to optimize thedisposing of the screen printable material onto the substrate and uponto the various elevated surfaces or levels that the screen printablematerial is to be disposed.

Furthermore, the screen used in disposing screen printable material inaccordance with the present invention is preferably provided withopenings, or patterns, that are geometrically configured to compensatefor the “uphill” portion or region of the structure to be formed. Forexample, if a conductive trace is to have a generally constant widthalong its longitudinal axis, including that portion of the trace whichrises from a first level to a second higher or elevated level, it may benecessary to reduce the width of the corresponding opening in the screento compensate for distortions that may occur in the transition from onelevel to the next level of the conductive trace to be formed. Toillustrate, it may be necessary to reduce the width of the opening inthe screen corresponding to the “uphill” portion of the conductive traceto compensate for the screen printable material's propensity toundesirably disperse laterally beyond the desired width that the“uphill” portion of the conductive trace is to have. In other words, thescreen printable material or paste may flow outwardly or bulge on one orboth sides of the “uphill” region and thereby possibly come into contactwith proximately located conductive traces if the corresponding portionof the opening in the screen is not reduced in width to compensate forthe tendency to bulge or spread. This unwanted lateral distortion couldbe particularly troublesome when using materials or pastes of highviscosity to form traces or other structures that are to be very closelypositioned with respect to each other. Such a case could occur whenforming thick film conductive traces that are to have a center-to-centerspacing or pitch, ranging in the magnitude of a few mils to 10 mils(0.010 inches/0.254 mm) or more.

The uphill screen printing of the present invention is particularlysuitable for simultaneous formation of conductive traces on severalareas of a common substrate in a high-quantity, high-speed productionenvironment in which the substrate will eventually be segmented into amultitude of individual microelectronic device sub-components. Forexample, a preselected number of individual areas preferably arranged inan array of a selected pattern on a substrate, such as by a preselectednumber of rows and columns, can have a number of screen printingoperations performed thereon, including the screen printing ofconductive traces or other structures, in accordance with the presentinvention. Upon the completion of the last operation that is to beperformed on each of the individual areas or array of areas located onthe common substrate, the individual areas of the array are thensegmented into individual substrates which will eventually serve as anindividual component in a FED device, for example.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a cross-sectional view of a portion of an exemplarymicroelectronic component provided with conductive traces formed bysuccessive screen printing operations and then joined via a wire bond inaccordance with the prior art;

FIGS. 1B-1C are cross-sectional views illustrating a representative,prior known screen printing method for forming conductive traces on aportion of the representative microelectronic component of FIG. 1A;

FIGS. 2A-2D are cross-sectional views illustrating the screen printingof an exemplary conductive trace on a portion of a representativemicroelectronic component in accordance with the present invention;

FIG. 3A is plan view illustrating a representative microelectroniccomponent in which exemplary conductive traces have been disposed on aportion thereof in accordance with the present invention;

FIG. 3B is a cross-sectional view taken along line 3B—3B of a selectedportion of the representative microelectronic component illustrated inFIG. 3A;

FIG. 3C is an enlarged plan view depicting a representative, isolatedportion of the microelectronic component including two laterallyadjacent conductive traces as illustrated in FIG. 3B;

FIG. 3D is a plan view showing the two conductive traces of FIG. 3C inisolation;

FIG. 3E is a plan view of an isolated portion of a necked-down openingor pattern formed through a screen and in which the necked-down portionthereof corresponds to the “uphill” region in which a generallyrectangular conductive trace, for example, is to make a transition to ahigher level, thus allowing the final conductive trace to have agenerally constant width along its longitudinal axis in accordance withthe present invention;

FIG. 4 is a plan view of a 3×4 array of certain layers of exemplarymicroelectronic components formed on a common, yet to be subdivided,substrate, wherein each component includes conductive traces disposedthereon in accordance with the present invention.

FIG. 5 is a cross-sectional view of a portion of a representativemicroelectronic component in which two different conductive traces havebeen disposed on a substrate and respective spacer elements of differingheights in accordance with the present invention;

FIG. 6 is a cross-sectional view of a portion of a representativemicroelectronic component in which one conductive trace is disposed upona spacer element having a plurality of levels in accordance with thepresent invention;

FIG. 7 is a cross-sectional view of a portion of a representativemicroelectronic component in which a pre-existing lower level conductivetrace is electrically connected to an elevated bond pad in accordancewith the present invention; and

FIG. 8 is an exploded perspective view of a simplified representativemicroelectronic assembly, such as a field emission display device,constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to drawing FIGS. 2A through 2D of the drawings, asubstrate 2, such as a transparent plate formed of borosilicate glass, aceramic substrate, or other substrate formed of a suitable material, ispositioned within a screen printing apparatus 18. Insulative ordielectric layers 4 and 6 are previously disposed onto substrate 2 at apreselected location by a preselected method, such as by screenprinting. In the case of constructing an anode plate for an exemplaryfield emission display device, for example, an insulative or dielectric,rail, spacer, ridge, or similar spacer structure 3, preferably comprisedof stacked layers 4 and 6, are positioned along at least one portion ofwhat is to be the display window of such a FED device. Typically,upper-most dielectric layer 6 will be micro-polished so that theupper-most surface, as oriented in drawing FIGS. 2A through 2D, will bereduced to a preselected height H above the upward facing surface ofsubstrate 2. Height H for an elevated structure or spacer 3, such asprovided on an anode plate to be used in a FED device, will typicallyrange from 3 to 5 mils (0.003 inches/0.008 cm-0.005 inches/0.013 cm).However H, as depicted in FIG. 2A, can range upwards of at leastapproximately 10 mils (0.010 inches/0.025 cm) with screen printingstructures in accordance with the present invention. Furthermore,although spacer 3 has been illustrated as being comprised of twodielectric layers, alternatively, a single layer or more than two layerscould be used to form a raised or elevated structure such as spacer 3.Furthermore, spacer 3 need not have insulative, dielectric qualities.Screen support frame 20 can be obtained from a number of commercialsources and is provided with a screen 30 which ranges in overall widthof about 20 inches (50 cm) and, for best results, will have a very thincross-sectional thickness ranging from approximately 0.0002 inches toapproximately 0.0007 inches (approximately 0.005 to approximately 0.0018cm).

Preferably, screen 30 is formed of an interwoven mesh material such asfine diameter stainless steel wire or a monofilament polyester which hasbeen woven to have a fine mesh value ranging from approximately 80 toapproximately 500 mesh. Typically, the fine steel wire or polyesterfilament will have a nominal diameter ranging from approximately 0.2mils to approximately 0.8 mils (0.0002 inches/0.0005 cm to 0.0008inches/0.0020 cm) with an approximate mesh range of 80-500. Screens ofsuitable material and mesh are commercially available from a number ofmanufacturers, including Rigsby Screen and Stencil, Inc., Torrance,Calif.; Utz Engineering, San Marcos, Calif.; and Micro-Screen, SouthBend, Ind.

As referred to within the art, “snap-off” distance d is the distance inwhich the bottom surface of screen 30 is ideally brought withinproximity of the back surface of substrate 2 which is to be screenprinted with a screen printable paste or substance, such as conductivepaste 34. In the case of screen printing a conductive trace, such aslower level portion 36 of a conductive trace shown partially disposed onsubstrate 2 in drawing FIG. 2A, a snap-off distance d, ranging fromabout 0.1 mils (0.00025 inches/0.00064 cm) to 0.125 mils (0.000125inches/0.000317 cm), has been demonstrated to work very well. However,depending on rheological characteristics of the screen printablesubstance or paste to be applied to substrate 2, a greater snap-offdistance ranging upwards of 0.125 mils (0.000125 inches/0.000317 cm) canalso be used depending upon the overall dimensions, geometry, andspacing of the structures to be screen printed. In some applications,the screen may actually contact the substrate and other structures to bescreen printed, and such contact may not necessarily negatively affectthe quality of the final screen printed structure.

Preferably, for screen printing conductive traces onto a glass substrateand up onto an insulative spacer having a height H ranging upwards of 10mils (0.010 inches/0.025 cm), a screen printable electrically conductivepaste material having a viscosity ranging between 50,000 and 600,000centipoise is suitable. A viscosity in the range of 250,000 to 400,000centipoise is preferred when screen printing closed-spaced structuresonto two or more levels, such as when screen printing conductive tracesonto a spacer having a top-most surface with a height betweenapproximately 3 to 5 mils (0.003 inches/0.008 cm to 0.005 inches/0.013cm) from the substrate in which it is disposed upon.

As depicted in drawing FIG. 2A, there are three different anglesidentified with respect to screen 30 and the substrate being printed.Angle α, is the angle formed between the bottom of screen 30 behindsqueegee 32 and the upwardly facing surface of substrate 2. Angle β isthe angle formed between the bottom of screen 30 ahead of squeegee 32and the upwardly facing surface of substrate 2. Angle δ is the angleformed between the bottom of screen 30 ahead of squeegee 32 and thetop-most surface of spacer 3, which in drawing FIG. 2A would be thetop-most exposed surface of layer 6.

As shown in drawing FIG. 2B, squeegee 32 is continuously biased downwardand is preferably drawn in the direction of the arrow across the screenat a constant speed ranging between 0.25 inches per second and 3.00inches per second, with a speed of approximately 0.75 inches per secondbeing particularly suitable. Furthermore, squeegee, wiper, or blade 32preferably has a generally triangular-shaped cross-sectional areaterminating into a point, and preferably has an angle Θ (as depicted inFIG. 2A) in the range of 30° to 120°, with an angle Θ of approximately45° being particularly suitable for forming a wide variety ofdifferently shaped conductive traces up onto structures of variousheights, such as spacer structures, frequently called for whenconstructing precisely dimensioned and configured electrical circuits onsubstrate components used in FED devices when screen printing aconductive trace onto at least one lower surface and at least one higheror elevated surface having a height ranging between 3 to 5 mils (0.003inches/0.076 mm to 0.005 inches/0.127 mm), if not upwards of 10 mils(0.010 inches/0.254 mm) from the lower surface.

As squeegee 32 traverses substrate 2, the various angles α, β, and δwill change slightly due to frame 20 being fixed in relation tosubstrate 2. Thus, each angle α, β, and δ is respectively designatedwith a single prime (′) and a double prime (″) in FIGS. 2B and 2C toshow such slight variations of angle as the screen printing progressesin a preferably continuous manner.

Generally, angle δ, including any slight variations from the nominalvalue thereof, i.e., the angle formed between the bottom surface ofscreen 30 and the top surface of layer 6 of spacer 3, which preferablywill be a planar surface as shown in FIGS. 2A through 2D, preferablyshould be maintained within a value of approximately 5 to 10 degrees toprovide the best results when practicing the present invention. However,it should be understood that it may be necessary or preferred tomaintain an angle which is less than, or, alternatively, more than, thepreferred range in order to accommodate specific structures orgeometries while screen printing various structures having at least oneor more levels.

Illustrated in drawing FIG. 2B, in particular, is the “uphill” portion38 of the conductive trace being formed as squeegee 32 approaches theleft-hand portion of spacer 3. Preferably, angle δ, and any slightvariations thereof, is maintained within the preferred range ofapproximately 5 to 10 degrees to provide the best results, particularlywhen applying uphill portion 38 of the exemplary conductive trace. Bycarefully maintaining screen print angle δ within the preferred range,the unwanted tendency for conductive paste 34 to be laterally dispersedwill be minimized, if not prevented. Furthermore, it is suggested thatrelatively soft squeegee 32 be biased toward substrate 2 withsignificantly more pressure than when using conventional screen printingtechniques to further minimize the potential for unwanted dispersion ofconductive paste 34, especially when disposing uphill portion 38. It isfurther suggested that screen 30 be stretched very tightly within frame20 of screen printing apparatus 18, and to a certain extent, also by wayof the downward bias of squeegee 32, so as to form a tight sealing“gasket” around the particular area or pattern in which screen printableconductive paste 34 is being disposed onto substrate 2 and upwardly ontothe upper-most surface of spacer 3.

Illustrated in drawing FIG. 2C is the continuing application of screenprintable paste 34 on the upper-most surface of layer 6 of spacer 3 toform a second or upper-level portion 40 of the exemplary conductivetrace. That is, the first or lower-level portion 36 has already beendisposed on substrate 2, as has uphill portion 38, and against the sideof layers 4 and 6. As can be seen in the cross-sectional view of drawingFIG. 2C, the exemplary conductive trace is continuous and uninterruptedand has been formed in a single, continuous sweep of squeegee 32 acrosspatterned screen 30. Forming a conductive trace which extends from afirst level to a second level in such a single-step offers a significantsavings with respect to production time and associated fabricationcosts, especially when compared to the prior art method of wire bondingas illustrated in drawing FIGS. 1A through 1C of the drawings.

Illustrated in drawing FIG. 2D is the fully formed conductive trace 42with squeegee 32 and screen 30 being vertically withdrawn from substrate2 and spacer 3 on which conductive trace 42 now resides in wet form. Atthis point, substrate 2 would likely be removed from screen printingapparatus 18 and placed in an oven wherein conductive trace 42 would be“fired” or, in other words, dried. After exposing substrate 2 toelevated temperatures in order to fire conductive trace 42, substrate 2could be prepared for further processing, including additional screenprinting or being assembled with other components, to ultimately form aFED device.

Illustrated in drawing FIG. 3A is a top view of an exemplary, simplifiedanode plate 44 of a FED device having an insulative spacer 3 having aplurality of conductive traces 42 formed on a substrate 2 and uponinsulative layer 6 of ridge 3 which is positioned along the left side ofanode plate 44. Conductive traces 42 are formed in accordance with thepreceding description and as shown in drawing FIGS. 2A through 2D. Outerlocated, end-most conductive traces 42A and 42B shown in drawing FIG. 3Adiffer from intervening traces 42 in that only end traces 42A and 42Bhave outwardly facing alignment tabs. Insulative layer 4 can be screenprinted onto substrate 2 to provide a raised insulative border about theperiphery of anode plate 44. Opposite of ridge or spacer 3 is anotherridge or spacer 7, also comprised of screen printed insulative layers 4and 6.

Illustrated in drawing FIG. 3B is a representative cross-sectional viewof anode plate 44 as taken along line 3B—3B of drawing FIG. 3A. In thecross-sectional view of drawing FIG. 3B, conductive trace 42, having anominal vertical thickness of t, extends from the left edge of substrate2, extends over the top-most surface of layer 6, which, as previouslydescribed, in combination with layer 4, comprises insulative spacer 3having a preselected height H. Oppositely positioned spacer 7, comprisedof layers 4 and 6, is located on the right side of substrate 2 as shownin drawing FIGS. 3A and 3B and will usually be provided with the samepreselected height H so that a complementary cathode plate 50 will bepositioned so as to span across the insulative spacers 3 and 7 as shownin a simplified manner in the perspective view of drawing FIG. 8, makingelectrical contact with the various contact portions of conductivetraces 42, including end traces 42A and 42B, having respectively shapedgeometries for alignment purposes, located atop layer 6 of spacer 3. Inoperation, transparent area 45 will ultimately serve as the viewingwindow for the FED device. Optional contact pads can be provided on topof spacer 7 (not shown) if desired. Furthermore, oppositely positionedconductive traces could be disposed on spacer 7 in accordance with thepresent invention.

Returning to FIGS. 3A through 3E, as illustrated, the exemplaryconductive traces formed by the uphill screen printing process of thepresent invention can have geometries of various shapes and sizes, andbe located from each other within a wide range of spacing distances, aswell as with respect to other nearby structures.

Drawing FIGS. 3C and 3D, in particular, show in enlarged detail theexemplary conductive traces 42, including 42A and 42B, to be provided onexemplary anode plate 44 of a representative FED device as discussed andillustrated herein. Such provides a non-limiting example of the precisedimensioning and spacing of screen printed structures that can bedisposed onto multiple levels of a work piece, such as a generallyplanar substrate 2 made of suitable glass or ceramic material, up ontoan elevated structure, such as spacer 3 formed of insulative layers 4and 6. Exemplary dimensions and spacing or, as referred to in the art,the pitch between conductive traces or pads, are depicted in drawingFIG. 3D. In drawing FIG. 3D, upper portions of conductive trace 42 havea generally rectangular profile extending along an imaginary centerlineCL and further have a narrower width W1 and a relatively wider width W2.Furthermore, upper-level portion 40 of conductive trace 42 has a lengthL1. The proximately positioned conductive trace having a modified upperportion 42A is provided with an outwardly extending tab portion having awidth W3, a tab extension length E, and an offset length L2. By way ofexample, the various dimensions can be sized as follows. Length L1 canbe approximately 24.1 mils (0.0241 inches/0.0612 cm), a width W1 ofapproximately 8.0 mils (0.008 inches/0.020 cm), a width W2 ofapproximately 12.0 mils (0.012 inches/0.0304 cm), a width W3 ofapproximately 8.0 mils (0.008 inches/0.020 cm), an extension length E ofapproximately 6.0 mils (0.006 inches/0.015 cm), a length L2 ofapproximately 4.0 mils (0.004 inches/0.010 cm), and acenterline-to-centerline spacing or pitch of 20 mils (0.020 inches/0.050cm). Region 5 denotes the uphill, or elevational transition, area of theconductive traces.

By way of example, the two particular traces shown in FIG. 3D werescreen printed in accordance with the present invention to a “wet” depthof approximately 0.5 mils (0.0005 inches/0.0013 cm) in verticalthickness or height, approximately 6 mils (0.006 inches/0.015 cm) innominal width, and having a pitch in spacing of approximately 20 mil(0.020 inch/0.05 cm). The particular electrically conductive paste usedis a gold based, screen printable paste available from a number ofcommercial suppliers such as IMR Corporation, having a preferredviscosity of approximately 250,000 to 400,000 centipoise. Upon firingthe substrate in an oven, the nominal thickness of the exemplaryconductive traces was reduced to approximately 0.2 mils (0.0002inches/0.0005 cm).

The preceding example is provided herein to illustrate that the subjectmethod of screen printing is readily capable of producing small,well-defined structures, such as conductive traces 42, 42A, and 42B,extending between at least two levels, and other such screen printedstructures particularly useful in the production of microelectronicdevices such as FED devices.

Furthermore, the acceptable range of viscosity for a given screenprintable substance or paste will be significantly influenced by overallthickness or height, length, width, and spacing or pitch, with respectto other traces that are to be simultaneously formed of the screenprintable material and are positioned to be in close proximity to eachother.

Referring now to drawing FIG. 3E, wherein a representative opening orpattern 36′ has been formed in screen 30 to have a preferredconfiguration in order to minimize the amount of any unwanted distortionin printing the “uphill” portion 5 of a screen printable structure, suchas conductive trace 42, on a substrate 2 as illustrated in other FIGS.of the drawings. In particular, opening 36′ has a nominal width W1′which corresponds to the nominal width W1 that lower portion 36 of agiven conductive trace 42 is to have. In the preceding example, W1 ofconductive trace 42 is approximately 8 mils (0.008 inches/0.203 mm)across. Thus, for lower-level portion 36 of conductive trace 42 that isto be screen printed onto the preferably generally planar substrate 2,the corresponding region in screen 30 would also have a nominal widthW1′ of approximately 10 mils (0.010 inches/0.025 cm) across. Whenprinting the “uphill” portion of lower-level portion 36 of a structure,such as conductive trace 42, there may be a tendency of the screenprintable material to disperse laterally or bulge, and thereby possiblycontact or touch other structures positioned nearby, such as aneighboring conductive trace 42. Of course the predisposition towardsuch unwanted dispersal or bleeding will be influenced by ambientconditions such as temperature and pressure, the vertical distance orheight H in which the conductive trace is to extend up to, and theviscosity of the particular screen printable material being printed, thenominal thickness of the screen, the snap-off distance d, the softnessof the squeegee, and whether or not the screen may be sufficientlybiased against the workpiece to be screen printed so as to create asuitable seal or “gasket” about the area in which the screen printablematerial is to be applied. Thus, to prevent, or at least minimize, suchunwanted lateral dispersal or bulging when working with relatively lowviscosity screen printable material, such as low viscosity gold basedconductive paste, and when forming particularly small, closely spacedstructures that are to extend vertically for significant verticaldistance or height, it is preferred that the corresponding width W1″ benarrowed or reduced at the particular region in which the screen printedstructure is to extend upwardly. In other words, in some cases it may bedesired to neck down the width of the opening 36′ where the uphillportion 38 of a conductive trace 42, for example, is to rise to the nextlevel in which upper-level portion 40 will be disposed. As an example,W1″ of screen opening 36′ was formed to have a gradually reducedconfiguration (as shown) to a nominal dimension of approximately 6 mils(0.006 inches/0.015 cm) in order to prevent any unwanted lateraldispersal from either side of “uphill” portion 38, with uphill portion38 rising to a height H between approximately 8 mils (0.008 inches/0.020cm) to 10 mils (0.010 inches/0.025 cm). The resulting conductive trace42 was screen printed with a conductive paste having a viscosity between250,000 to 400,000 centipoise. Of course, the various influencingfactors previously listed can be greater or less than the exemplaryranges provided, but it will now be apparent to those skilled in the artthat when adjusting one factor, one or more of the other factors can andmay need to be adjusted to optimally compensate for the particularstructure to be formed without going beyond the scope of the presentinvention.

Drawing FIG. 4 depicts a plan view of a yet to be segmented glasssubstrate 2 comprising a plurality of what will eventually be individualanode plates 44, each having insulative spacers comprised of layers 4and 6, as well as screen printed conductive traces 42, 42A, and 42Bextending from substrate 2 upward onto layer 6 as previously illustratedand described herein. The particular array 46 shown in drawing FIG. 4 isreferred to as a 3×4 array due to substrate 2 having three rows and fourcolumns of what will eventually be twelve individual anode plates 44.Upon all screen printing operations being performed on substrate 2,including the “uphill” screen printing of conductive traces 42, optionalend-most traces 42A, 42B, in accordance with the present invention, andany firing that may be required, substrate 2 is segmented by scoring orcleaving 48, or any other suitable method for separating substrate 2into twelve individual anode plates 44. Segmented anode plates 44 willthen, in due course, be assembled with respective complementary cathodeplates, such as cathode plate 50 illustrated in drawing FIG. 8, therebyproviding twelve individual exemplary FED devices. As will now beapparent, smaller or larger arrays of FED devices or othermicroelectronic devices can be screen printed in accordance with thepresent invention, limited only by the size of the screen that can beaccommodated by the particular screen printing equipment being used andthe size of the microelectronic component or components being producedon a given common substrate of suitable material. Thus, it can beappreciated that embodiments of the disclosed screen printing method areparticularly suitable for implementation within a variety of productionlines used for screen printing of microelectronic devices, including,but not limited to, FED devices.

Drawing FIGS. 5, 6 and 7 further illustrate the suitability andadaptability of the present invention for the screen printing of screenprintable structures, such as multi-level conductive traces, onto asubstrate having insulative structures, such as spacers or ridges, ofdiffering heights and configurations.

Substrate 2 of drawing FIG. 5 has a first rectangularly shapedinsulative ridge or spacer 52 having a vertical height H1. Proximate tofirst ridge or spacer 52 is a second, taller rectangularly shaped ridgeor spacer 54. As can be seen on the left side of drawing FIG. 5, a firstscreen printed structure, such as a conductive trace 56 having an uphillportion 58, has been screen printed onto substrate 2 and up onto thetop-most planar structure, such as an insulative spacer 52. A secondscreen printed structure 60, also exemplified as being a conductivetrace, extends from substrate 2 upward and to the right having an uphillportion 62 onto the top-most surface of second spacer 54 having avertical height H2, which, in this particular illustration, happens tobe greater than vertical height H1 of first spacer structure 52. Thepreferred direction in which the squeegee travels across the screen (notshown in drawing FIG. 5) is denoted. Conversely, the first and secondspacers 52 and 54 could be transposed in position. That is, tallerspacer 54 could be located on the left side of substrate 2 and likewise,shorter spacer 52 could be located on the right side of substrate 2 ifdesired.

In drawing FIG. 6 a representative substrate 2 is shown having a firstspacer 70 of a generally rectangular cross-section, and a second smalleradditional spacer 72, also of a generally rectangular cross-section.Second spacer 72 is off-settingly positioned on top of first spacer 70to create a ledge or shelf, which results in spacers 70 and 72 having acombined height H2 as measured from the top-most surface of substrate 2.A screen printed structure, such as a conductive trace 74 screen printedin accordance with the present invention, extends from the left side ofdrawing FIG. 6 generally upwardly and toward the right, up and thus ontothe top-most exposed surface of structure 70, exemplarily depicted as aninsulative spacer. Conductive trace 74 further extends generallyupwardly and toward the right so as to be disposed onto the top-mostsurface of structure 72, also exemplarily depicted as being aninsulative spacer. As with drawing FIGS. 5 and 7, the preferreddirection of squeegee travel is shown proceeding from left to right withthe vertical distance H2 having a maximum dimension of at leastapproximately 10 mils (0.010 inches/0.025 cm). Thus, conductive trace 74of drawing FIG. 6 has two uphill portions 76 and 78, thereby providingan example of a continuous, multi-level, screen printed conductive traceor structure 74 disposed upon a substrate 2 and extending to thetop-most surface of multi-level or stepped spacer 72 in accordance withthe present invention.

The illustration of drawing FIG. 7 depicts an exemplary substrate 2having a first structure, such as an insulative ridge or spacer 80having a generally rectangular cross-section which, in turn, has asecond smaller structure, such as contact or bond pad 82, positionedthereon resulting in a stacked vertical height of H2. Furthermore,substrate 2 has a generally planar rectangular structure such asconductive trace 84 disposed thereon such as by screen printing or othermethods known within the art. Uphill screen printed trace 86 is disposedon at least a portion of the exposed upward facing surface of conductivetrace 84 and is generally upwardly disposed from the right up onto thetop-most exposed surface of contact or bond pad 82. Thus, continuous,uphill screen printed conductive trace 86 is provided with an uphillsection 88 in accordance with the present invention, thereby providing acontinuous screen printed trace 86 which electrically connects trace 84located on the left side of drawing FIG. 7 with the upper-most surfaceof contact or bond pad 82. Therefore, conductive trace 86 being screenprinted in accordance with the present invention provides a practical,cost-effective alternative to prior known wire bonding of two or moreconductive traces or elements together to provide an electrical paththerebetween.

It can further be appreciated that the screen printing process of thepresent invention can be utilized to provide a very large variety ofscreen printable structures which are to span across and/or upward ontoat least one or more levels of a substrate having a wide variety ofdifferent shaped elevated structures thereon. It is also to beappreciated that the subject method of screen printing is suitable forforming structures which extend over and against at least one verticalside of a subject structure. For example, in addition to the exemplarystructures disclosed herein having generally vertical sides that aregenerally perpendicular to the underlying substrate, structures havingsides which are sloping, angled, curved, stepped, and other irregularshapes, are suitable candidates in which a screen printed structure canbe disposed upon in accordance with the present invention.

Lastly, drawing FIG. 8 illustrates an exemplary anode plate 44 havingconductive traces screen printed thereon in accordance with the presentinvention as discussed previously herein. Insulative spacer 3 as shownis generally rectangular, that is, spacer 3 is formed of insulative,dielectric layers 4 and 6 that have generally vertical side walls asillustrated in other drawing FIGS. As mentioned herein, in the contextof manufacturing a FED device, a cathode plate 50 will typically beinstalled upon ridges or spacers 3 and 7 so as to be precisely spacedaway from anode plate 44 by a preselected distance, yet will also beplaced into electrical contact with the various conductive traces 42,including optional end-most traces 42A and 42B. Furthermore, oppositelypositioned bond pads or electrical contacts 9 may be provided on theupper-most surface of insulative spacer 7, comprised of stackedinsulative layers 4 and 6, if desired. Transparent area 45 of anodeplate 44 will typically be the back side of the transparent viewing areaupon the FED device being completely assembled.

Although the foregoing description contains many specifics, these shouldnot be construed as limiting the scope of the present invention, butmerely as providing illustrations of some of the preferred and exemplaryembodiments. Similarly, other embodiments of the invention may bedevised which do not depart from the spirit or scope of the presentinvention. The scope of this invention is, therefore, indicated andlimited only by the appended claims and their legal equivalents, ratherthan by the foregoing description. All additions, deletions andmodifications to the invention as disclosed herein which fall within themeaning and scope of the claims are to be embraced thereby.

1. A method of forming at least one electrically conductive trace on asubstrate comprising: providing a substrate having at least one face andhaving a dielectric structure of a preselected configuration formed onthe at least one face of the substrate, the dielectric structure havingat least one first surface vertically distanced from the substrate;providing a print screen having a first side and a second side andpositioning the second side of the print screen opposite the at leastone first surface of the dielectric structure of the substrate;providing and biasing a squeegee of a preselected hardness against thefirst side of the print screen toward the substrate, thereby forming anangle between at least a portion of the second side of the print screenforward of the squeegee and the at least one first surface of thedielectric structure; screen printing an electrically conductivesubstance onto the at least one face of the substrate located below theat least one first surface of the dielectric structure to form at leastone electrically conductive trace; screen printing the electricallyconductive substance onto at least a portion of the at least one firstsurface of the dielectric structure so as to further form and extend theat least one electrically conductive trace from the substrate to the atleast one first surface of the dielectric structure; limiting the angleformed between the at least a portion of the second side of the printscreen and the at least one first surface of the dielectric structure toan angle not exceeding approximately 15° while screen printing the atleast one first surface of the dielectric structure; and firing thesubstrate.
 2. The method of claim 1, wherein firing the substrateincludes firing the substrate upon forming the at least one electricallyconductive trace in its entirety.
 3. The method of claim 2, wherein theat least one electrically conductive trace has a nominal depth when wetnot exceeding approximately 0.7 mil (0.0007 inches/0.0018 cm) and anominal depth upon being fired not exceeding approximately 0.5 mil(0.0005 inches/0.0013 cm).
 4. The method of claim 3, wherein the atleast one electrically conductive trace comprises a plurality ofelectrically conductive traces arranged in a generally parallel spacedrelationship having a preselected pitch not exceeding approximately 50mils (0.050 inches/0.127 cm).
 5. The method of claim 4, furthercomprising at least one of the plurality of electrically conductivetraces formed and extending from the at least one face of the substrateonto the dielectric structure being formed to terminate into a generallyrectangularly shaped contact pad located on the at least one firstsurface of the dielectric structure.
 6. The method of claim 5, whereinthe plurality of electrically conductive traces includes oppositelypositioned end-most located electrically conductive traces, eachend-most located electrically conductive trace being formed torespectively terminate into the generally rectangularly shaped contactpads located on the dielectric structure and comprising tabular-shapedextensions extending laterally outwardly from the respective generallyrectangularly shaped contact pads.
 7. The method of claim 6, wherein thesubstrate comprises at least one anode plate of a field emission displaydevice.
 8. The method of claim 7, wherein the substrate comprises aplurality of anode plates arranged in an array.
 9. The method of claim6, wherein each of the plurality of electrically conductive tracescomprises an uphill region intermediate the at least one face of thesubstrate and the dielectric structure and wherein the uphill region iscontiguous with at least a portion of a generally vertically extendingsidewall of the dielectric structure.
 10. The method of claim 1, whereinthe at least one electrically conductive trace is formed on thedielectric structure subsequent to the at least one electricallyconductive trace being formed on the substrate.
 11. The method of claim10, wherein the print screen comprises stainless steel or monofilamentpolymer fiber and wherein the print screen has a mesh within a range ofapproximately 80 to approximately 500 and a nominal thickness notexceeding approximately 0.8 mils (0.0008 inches/0.0020 cm).
 12. Themethod of claim 11, wherein the squeegee has a durometer value within arange of approximately 50 to
 70. 13. The method of claim 1, wherein theelectrically conductive substance has a viscosity within a range ofapproximately 50,000 to 600,000 centipoise and further comprises gold.14. The method of claim 1, wherein the angle formed between the at leasta portion of the second side of the print screen and the at least onefirst surface of the dielectric structure is limited to within a rangeof approximately 5° to approximately 10°.
 15. The method of claim 1,wherein the substrate comprises at least one of the group comprisingglass and ceramic and wherein the vertical distance of the at least onefirst surface of the dielectric structure from the at least one face ofthe substrate does not exceed approximately 10 mils (0.010 inches/0.025cm).
 16. The method of claim 15, wherein the dielectric structurecomprises a generally rectangular cross-section comprising at least onegenerally planar side surface extending generally perpendicular to theat least one face of the substrate and the at least one first surface ofthe dielectric structure is generally rectangular in shape.
 17. Themethod of claim 16, wherein the dielectric structure comprises at leasttwo vertically stacked layers of dielectric material.
 18. The method ofclaim 16, wherein the at least one first surface of the dielectricstructure has a width less than approximately 10 mils (0.010inches/0.025 cm) and the vertical distance of the at least one firstsurface from the substrate does not exceed approximately 7 mils (0.007inches/0.018 cm).
 19. The method of claim 16, wherein the at least oneelectrically conductive trace comprises a plurality of electricallyconductive traces arranged in a generally parallel spaced relationshipof a preselected pitch.
 20. The method of claim 19, wherein thepreselected pitch comprises a distance not exceeding approximately 50mils (0.050 inches/0.127 cm).
 21. The method of claim 20, wherein thepreselected pitch comprises a distance of approximately 20 mils (0.020inches/0.051 cm).
 22. The method of claim 16, wherein the at least oneelectrically conductive trace has a nominal depth not exceedingapproximately 1 mil (0.001 inches/0.0025 cm).
 23. The method of claim 1,further comprising maintaining a snap-off distance generally notexceeding approximately 0.2 mil (0.0002 inches/0.0005 cm) between thesecond side of the print screen and at least a portion of the at leastone face of the substrate when screen printing the electricallyconductive substance onto the at least a portion of the at least oneface of the substrate located below the at least one first surface ofthe dielectric structure to form the at least one electricallyconductive trace.
 24. The method of claim 23, wherein the snap-offdistance is maintained within a range of approximately 0.1 mils (0.0001inches/0.0003 cm) to approximately 0.125 mils (0.000125 inches /0.000317cm).
 25. The method of claim 1, wherein limiting the angle formedbetween the at least a portion of the second side of the print screenand the at least one first surface of the dielectric structure comprisesbeing limited to a range of approximately 5°.
 26. A method of forming atleast one electrically conductive trace on a substrate using a printscreen and a squeegee, the substrate having at least one face and havinga dielectric structure having a configuration formed on the at least oneface of the substrate, the dielectric structure having at least onefirst surface vertically distanced from the substrate, the print screenhaving a first side and a second side, the squeegee having a hardness,the method comprising: screen printing an electrically conductivesubstance onto the at least one face of the substrate located below theat least one first surface of the dielectric structure to form at leastone electrically conductive trace; screen printing the electricallyconductive substance onto at least a portion of the at least one firstsurface of the dielectric structure so as to further form and extend theat least one electrically conductive trace from the substrate to the atleast one first surface of the dielectric structure; limiting an angleformed between at least a portion of the second side of the print screenand the at least one first surface of the dielectric structure to anangle not exceeding approximately 15° while screen printing the at leastone first surface of the dielectric structure; and firing the substrate.27. The method of claim 26, wherein the at least one electricallyconductive trace is formed on the dielectric structure subsequent to theat least one electrically conductive trace being formed on thesubstrate.
 28. The method of claim 27, wherein the at least oneelectrically conductive trace has a nominal depth when wet not exceedingapproximately 0.7 mil (0.0007 inches/0.0018 cm) and a nominal depth uponbeing fired not exceeding approximately 0.5 mil (0.0005 inches/0.0013cm).
 29. The method of claim 28, wherein the at least one electricallyconductive trace comprises a plurality of electrically conductive tracesarranged in a generally parallel spaced relationship having apreselected pitch not exceeding approximately 50 mils (0.050inches/0.127 cm).
 30. The method of claim 29, further comprising atleast one of the plurality of electrically conductive traces formed andextending from the at least one face of the substrate onto thedielectric structure being formed to terminate into a generallyrectangularly shaped contact pad located on the at least one firstsurface of the dielectric structure.
 31. The method of claim 29, whereinthe plurality of electrically conductive traces includes oppositelypositioned end-most located electrically conductive traces, eachend-most located electrically conductive trace being formed torespectively terminate into the generally rectangularly shaped contactpads located on the dielectric structure and comprising tabular-shapedextensions extending laterally outwardly from the respective generallyrectangularly shaped contact pads.
 32. The method of claim 31, whereinthe substrate comprises at least one anode plate of a field emissiondisplay device.
 33. The method of claim 32, wherein the substratecomprises a plurality of anode plates arranged in an array.
 34. Themethod of claim 31, wherein each of the plurality of electricallyconductive traces comprises an uphill region intermediate the at leastone face of the substrate and the dielectric structure and wherein theuphill region is contiguous with at least a portion of a generallyvertically extending sidewall of the dielectric structure.
 35. Themethod of claim 26, wherein the electrically conductive substance has aviscosity within a range of approximately 50,000 to 600,000 centipoise.36. The method of claim 35, wherein the print screen comprises stainlesssteel or monofilament polymer fiber and wherein the print screen has amesh within a range of approximately 80 to approximately 500 and anominal thickness not exceeding approximately 0.8 mils (0.0008inches/0.0020 cm).
 37. The method of claim 36, wherein the squeegee hasa durometer value within a range of approximately 50 to
 70. 38. Themethod of claim 26, wherein the angle formed between the at least aportion of the second side of the print screen and the at least onefirst surface of the dielectric structure is limited to within a rangeof approximately 5° to approximately 10°.
 39. The method of claim 26,wherein the substrate comprises at least one of the group comprisingglass and ceramic and wherein the vertical distance of the at least onefirst surface of the dielectric structure from the at least one face ofthe substrate does not exceed approximately 10 mils (0.010 inches/0.025cm).
 40. The method of claim 39, wherein the dielectric structurecomprises a generally rectangular cross-section comprising at least onegenerally planar side surface extending generally perpendicular to theat least one face of the substrate and the at least one first surface ofthe dielectric structure is generally rectangular in shape.
 41. Themethod of claim 40, wherein the dielectric structure comprisesvertically stacked layers of dielectric material.
 42. The method ofclaim 40, wherein the at least one first surface of the dielectricstructure has a width less than approximately 10 mils (0.010inches/0.025 cm) and the vertical distance of the at least one firstsurface from the substrate does not exceed approximately 7 mils (0.007inches/0.018 cm).
 43. The method of claim 40, wherein the at least oneelectrically conductive trace comprises a plurality of electricallyconductive traces arranged in a generally parallel spaced relationshiphaving a preselected pitch.
 44. The method of claim 43, wherein thepreselected pitch comprises a distance not exceeding approximately 50mils (0.050 inches/0.127 cm).
 45. The method of claim 44, wherein thepreselected pitch comprises a distance of approximately 20 mils (0.020inches/0.051 cm).
 46. The method of claim 40, wherein the at least oneelectrically conductive trace has a nominal depth not exceedingapproximately 1 mil (0.001 inches/0.0025 cm).
 47. The method of claim26, further comprising maintaining a snap-off distance generally notexceeding approximately 0.2 mil (0.0002 inches/0.0005 cm) between thesecond side of the print screen and at least a portion of the at leastone face of the substrate when screen printing the electricallyconductive substance onto the at least a portion of the at least oneface of the substrate located below the at least one first surface ofthe dielectric structure to form the at least one electricallyconductive trace.
 48. The method of claim 47, wherein the snap-offdistance is maintained within a range of approximately 0.1 mils (0.0001inches/0.0003 cm) to approximately 0.125 mils (0.000125 inches/0.000317cm).
 49. The method of claim 26, wherein limiting the angle formedbetween the at least a portion of the second side of the print screenand the at least one first surface of the dielectric structure comprisesbeing limited to a range of approximately 5°.